Abstract

The effect of lattice termination on the surface states in a two-dimensional truncated photonic crystal slab is experimentally studied in a high-index-contrast silicon-on-insulator system. A single-mode silicon strip waveguide that is separated from the photonic crystal by a trench of variable width is used to evanescently couple to surface states in the surrounding lattice. It is demonstrated that the dispersion of the surface states depends strongly on the specific termination of the lattice.

Figures (3)

a, Transmission spectra (5-nm spectral resolution) for TE-polarized light of DT PhC waveguides with different trench widths. The red, magenta, blue, and black spectra correspond to nominal trench widths of 0.8a, 1.0a, 1.2a, and 1.2a, respectively. Spectra are shifted vertically by 3 dB
for clarity. Inset, field profiles of the TE mode in DT PhC waveguides with trench widths of 0.8a (image 1) and 1.2a (image 2). b, Photonic band diagrams calculated for the TE-like modes for the DT PhC waveguides with different trench widths. The red curve and the magenta, blue, and black open circles correspond to trench widths of 0.8a,1.09a,1.12a, and 1.17a, respectively. The dashed black curve represents the light line of the silica cladding layer.

a, High-resolution (0.5-nm) transmission spectra for TE polarization for waveguides with trench widths of 0.8a (red curve) and 1.17a (black curve). b, Magnified view of the photonic band diagram for the TE-like modes for a trench width of 1.17a. The solid (dashed) curves correspond to bands of even (odd) symmetry with respect to the xz plane bisecting the slab along the waveguide direction. Images
1–5 represent the in-plane magnetic field profiles calculated for corresponding frequencies marked 1–5
in the photonic band diagram.